Ultrafast excitonic saturable absorption in ion-implanted InGaAs/InAlAs multiple quantum wells

We report on ultrafast excitonic nonlinearities in ion-implanted InGaAs/InAlAs multiple quantum wells. We find that irradiation with energetic O+ and Ni+ ions can reduce the carrier lifetime from 1.6 ns down to 1.7 ps without significantly altering the excitonic absorption properties, making efficient fast saturable absorbers in the 1.3–1.5 μm wavelength range.